Book covers play a significant role in the marketing and success of the title. Despite being told never to judge a book by its cover, book covers are the first thing we notice when searching for something to read. Some covers are full of information, between the summary, blurbs, excerpts, and images; others are simplistic and bare, telling us nothing and leaving us to guess what lies within.
There are also trends in book covers. Covers made in the early 1990's for books appealing to teens were bright and usually featured ridiculous tag lines. YA titles now are simpler. There was a period of time when the covers would be photos of characters, to give us a picture of the people we would meet inside the pages. Then the trend seemed to shift to facial close-ups and then to only a portion of the face (eyes were a big draw apparently). Now there seems to be a push towards people's hands or feet; it also seems that every realistic teen book now has someone lying in the grass, although that is probably hyperbole.
So which covers are effective? What is being sold? What are publishers trying to gauge? It appears that the full image of a person limits our imagination; perhaps an eye or a hand or feet help us to put ourselves in the story?